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post #1 of 4 (permalink) Old 11-23-2009, 09:09 PM Thread Starter
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Resister Size - LED Install

Installed some new LED signals and tail light, and need some help identifying the proper resisters to install. Any recommendations?

Kit for tail light MAY have had resister included, however I've since lost the packaging (bought many months before install).

Thanks all!

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post #2 of 4 (permalink) Old 11-24-2009, 11:31 AM
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I'd assume the rear light would be ready to install as it comes, however the turn signal relay needs a certain minimum power to work properly and the LEDs are very low power devices.

Ideally if you can find out what power (W) they consume then you can use Ohm's law to calculate the required resistance to make up the rest up to the 10 watts per bulb that the relay is rated for.

Assuming they're are something like 2 watt per LED lamp, you'll need another 18 watts to make up the total normal load to the relay which is two 10w normal bulbs= 20 watts.

Using Resistance = V2/P

Take V as an average of 13 volts or so, and P the power you need to dissipate as 18 watts and we get 9.38 Ohms, use the nearest standard value of 10 Ohms with a 20 Watt rating at least.

You need to fit this resistor to just one of the turn signals, on both sides, either the front or rear as they're wired in parallel.

The most convenient type of power resistor from the point of view of ease of fitting and sturdiness would be the alloy-cased ones, like this:

You could instead fit a special not-load-dependant flasher relay. These are available for 20USD or so. I don't know if they're compatible with the Triumph's wiring and relay socket though. The people that sell LED turn signals should know about them.

Last edited by Forchetto; 11-24-2009 at 11:39 AM.
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post #3 of 4 (permalink) Old 11-24-2009, 06:03 PM
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Definitely go for the special flasher route(but thanks for the electronics lesson, Forchetto!). It's so much cleaner than splicing in even more unneeded wires. I can't find the thread right now, but someone referenced a cheap source on here a couple months ago. Flasher pin patterns are fairly universal. I think the stock triumph one is a standard 3 pin one. One pin is for the supply voltage(labeled "X" i think), one is for the load("L," the blinker lights), and the third is for the panel light("P"). With a 2 pin, X/L, the panel light(s) is(are) just piggy backed off of the blinkers themselves.

Here it is:

And here's one source posted there by DEcosse:
I'm sure you can tell them what type you pull off the bike and they'll know which model number you should order. It's about 1/3 of the way down the page.

Last edited by Verde; 11-24-2009 at 06:15 PM. Reason: found old links
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post #4 of 4 (permalink) Old 11-25-2009, 10:31 PM Thread Starter
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Thank you!!

Thank you! I'll repost what we end up with!

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